A Review of Regulation of Leaf Margin Development: Integrating Genetic, Hormonal, and Environmental Controls

Leaf margin morphology, encompassing entire, serrated, and lobed forms, is a key feature of leaf architecture with profound developmental, ecological, and evolutionary significance. This review synthesizes recent advances in understanding the regulation of leaf margin development, highlighting the integration of genetic, hormonal, and environmental cues. Central gene families such as cup-shaped cotyledon (CUC), Knotted1-like homeobox (KNOX), TCP, WOX, and LMI1/RCO are discussed in the context of their roles in promoting or restricting marginal growth. Hormonal regulators, particularly auxin, cytokinin, and gibberellin, interact through complex spatial feedback loops to fine-tune margin patterning, often mediated by key transporters, transcription factors, and miRNA modules. Age-dependent transitions, primarily regulated by the miR156-SPL pathway, modulate leaf margin complexity in both herbaceous and woody species. In addition to intrinsic genetic programs, extrinsic factors such as light intensity, temperature, nutrient availability, herbivory, and pathogen attack significantly influence margin development, demonstrating the plasticity of leaf morphology in response to environmental conditions. The integration of environmental signals into hormonal and gene regulatory networks enables plants to optimize leaf structure for photosynthesis, thermoregulation, and defense. This review also identifies emerging tools, such as spatial transcriptomics and genome editing, that promise to unravel the dynamic regulation of margin morphogenesis. By unifying developmental and environmental perspectives, we provide a conceptual framework for future studies on leaf form diversification and offer insights for potential applications in plant adaptation and crop improvement.